This Phase I STTR proposal will determine the feasibility of developing ambulatory systems to measure 3-dimensional body segment motion using a new spatial orientation sensor. This new spatial orientation sensor is referenced to the earth's magnetic field, it is non-inertial, self-calibrating, and are not constrained by some of the fundamental limitations of existing systems that measure orientation relative to the earth's magnetic field. This research will determine if these new spatial orientation sensors can achieve the performance level necessary to develop ambulatory motion analysis systems. Prototype sensors will be designed and fabricated. The accuracy, precision, and resolution of a prototype sensor will be determined. The performance of a prototype sensor will be evaluated in representative environments. The trade off between power requirements and frequency response will be evaluated in a sensor prototype. PROPOSED COMMERCIAL APPLICATION: A variety of potential commercial applications exist for systems utilizing these sensors to measure 3-dimensional body segment orientation. Configurations utilizing single or dual sensors could be used to measure joint range-of-motion, quantify tremor magnitude and frequency, and provide feedback of angular displacement during therapeutic exercise programs. Ambulatory systems utilizing multiple sensors could be used to assess gait and balance deficits in the elderly and persons with neurologic disease; monitor and document the progression of neurological, rheumatic, and musculoskeletal diseases and disorders; develop objective outcome measures of the efficacy of rehabilitation programs, surgical interventions, and drug treatments in human diseases and disorders that affect body movement; better understand the injury mechanisms associated with occupational, recreational, and sports activities; and assess the performance of activities of daily living, as well as occupational, recreational, and sports activities, in the environments in which they are typically conducted.